Effects Of Bacteria Protein(Methylococcus Capsulatus Bath) On Growth,Antioxidation And Inflammation Status Of Genetically Improved Farmed Tilapia(GIFT)(Oreochromis Niloticus)

Fish meal is known to be the main protein source in fish feed.Due to its overdependence,the commodity has become scares and very expensive,thereby threatening the sustainability of aquaculture production.Hence,identifying alternative protein sources that are sustainable and do not compromise fish growth is considered an urgent need in aquaculture.Recently,bacteria protein meal has gained popularity due to its nutritional composition that is similar to high quality fish meal.The purpose of the research was to assess the effects of increasing levels of bacterial protein(M.capsulatus,Bath)meal as a fish meal substitute with regards to growth performance,whole body composition,plasma parameters,enzymatic activities and expression of intestinal genes related to antioxidants and immunity response of juvenile genetically improved farmed tilapia(GIFT)(Oreochromis niloticus)for possible utilization in fish feeds.A total of 540 fish with an average weight of 3g were fed six diets for 56 days in which increasing levels of bacterial meal replaced fishmeal.Six iso-nitrogenous and iso-caloric experimental diets included 0 g/kg(control),17 g/kg,34 g/kg,54 g/kg,68 g/kg and 85 g/kg bacterial meal.Having completed the feeding trial,growth performance parameters such as weight gain rate(WGR),specific growth rate(SGR),feed intake(FI),feed conversation ratio(FCR),and survival rate(SR)of juvenile GIFT were significantly unaffected by fishmeal substitution(P>0.05).Plasma measurements such as immunoglobulin(Ig M)and albumin(ALB)significantly increased with an increase in bacteria meal in the diet(P<0.05),while intestinal enzymes including alanine aminotransferase(ALT),aspartate transaminase(AST),and alkaline phosphatase(ALP)were not significantly affected(P>0.05).Enzymatic activities of catalase(CAT),superoxide dismutase(SOD),glutathione peroxide(GPx)and glutathione(GSH)were also significantly unaffected by diet treatment(P>0.05).Total antioxidant capacity(T-AOC)in the highest bacterial protein inclusion rate increased significantly when compared to diet 1(control)while malondialdehyde(MDA)presented an opposite trend it decreased as bacteria protein meal increased(P<0.05).Antioxidants genes including nuclear factor erythroid 2-related factor 2(Nrf2)m RNA and glutathione peroxide 1(GPx-1)m RNA expression significantly decreased while total superoxide dismutase(T-SOD)m RNA increased with an increase in bacteria protein meal and later decreased(P<0.05).Pro-inflammatory including nuclear factor-kappa B(NF-κB),tumor necrosis factor-α(TNF-α),interfelony(IFN-γ)and interleukin8(IL-8)immunity genes strikingly decreased significantly as bacterial protein levels in the diet increased(P<0.05).Interleukin 1β(IL-1β)did not change significantly although numerically decreased with an increase in bacterial protein(P>0.05).Anti-inflammatory genes such as interleukin 10(IL-10)and interleukin 16(IL-16)had a similar trend with the pro-inflammatory genes(P<0.05).Based on the overall results obtained there is an indication that M.capsulatus,Bath can potentially be used as an alternative to fishmeal in the diet of the GIFT.